Vertical slicing machines for slicing flitches to produce thin sheets of veneer are well known in the art and examples of these types of machines are shown and described in U.S. Pat. Nos. 2,303,213; 3,905,408; 4,102,372; and 3,441,069. These machines include a flitch table mounted to a support structure. The flitch table reciprocates up and down at an incline to the vertical for reasons understood by those skilled in the art. A stationary knife slices the flitch as it travels downward. Once the flitch clears the knife on the downward stroke, the knife is retracted so that the flitch does not come into contact with the knife on the way back up. Next, the cutting blade is indexed inward a distance equal to the width of the next slice. A different approach in slicing is to have the stationary knife slicing as the flitch travels upward. On the downstroke, the knife is retracted to avoid touching the flitch. Before it starts moving upwards again it is indexed to the predetermined thickness. The flitch is typically held to the flitch table by a set of clamping dogs. In this manner the flitch is securely held while it travels up and down and engages the cutting blade. Accordingly, the flitch can be trimmed down only to a certain residual width. At this point, further slicing would cause contact between the cutting blade and the clamping dogs or other clamping apparatus which would result in damage to the blade. The systems for holding the flitches in place on the vertical machines include mechanical clamps which move to secure the flitch by means of rotating screws driven by electric motors or by means of hydraulic cylinders. Also, there are flitch tables which hold the flitches exclusively by vacuum generated through vacuum ports disposed throughout the entire surface of the table.
The mechanical clamps, motor driven or hydraulic, are capable of holding any type and shape of flitch. A combination of groups of clamps with different heights, ranging from 150 mm to 10 mm, allow the slicing of the flitches to a residual board of 12 mm. As described above, additional slicing would cause damage to the blade from contact with the clamping mechanisms. These mechanical systems can present a problem for the slicing operation. When the flitch becomes thin towards the end of the cutting, it starts to deflect away from the table, especially on wider flitches, which results in variations in the thickness of the veneer. The variations result because if the flitch is deflecting away, then it is extending further across the blade than is intended, and therefore the veneer will be too thick.
The vacuum flitch tables have the disadvantages that certain shapes or sizes of flitches cannot be safely clamped, and dropping the flitch during the cutting process can result in damages to the machine. Accordingly, this limits the use of the vertical slicing machine in some circumstances. Another approach has been to install a number of vacuum pockets in fixed positions along the flitch table in combination with mechanical systems. A drawback with this arrangement is the fact that the flitch has to be loaded exactly at the position where the pockets are located, otherwise, if the pocket is not covered, the vacuum ports will be open to the atmosphere and the vacuum will not operate on the flitch. It is relatively difficult to load the flitches properly with the typical manual loading systems used throughout the industry because the operators have to be very careful not to incline or move the flitches vertically out of the vacuum area. Also, different qualities of woods require a different cutting angle, and when the vacuum pockets are fixed on the table, it is necessary to move the setting in order to accommodate the alternate cutting angle which takes time.
Accordingly, what is needed is an apparatus for clamping flitches to flitch tables teat overcomes the drawbacks discussed above by combining the vacuum pockets with the hydraulic clamps.